A photoplethysmogram (PPG) signal can be obtained from a pulse oximeter, which employs a light emitter and a light sensor to measure the perfusion of blood to the skin of a user. The PPG signal can be compromised by noise due to motion (e.g., acceleration) artifacts. That is, movement of the body of a user can cause the skin and vasculature to expand and contract, introducing acceleration artifacts into the PPG signal. As a result, motion artifacts can make it difficult to effectively determine a user's heart rate.